Image forming device

Abstract

To inhibit a roll sheet from being placed in contact with an inkjet head by warpage of an end of the roll sheet.SOLUTION: An image formation device includes: a transport part which transports a roll sheet along a transport path in a transport direction; and an image formation part having an inkjet head which injects an ink to an image formed surface of the roll sheet transported by the transport part. The transport part has a pair of guide members 22 which guides the roll sheet at a position of ink injection by the inkjet head. In a direction X orthogonal to the transport direction, a guide width W1 in which the pair of guide members 22 guides the roll sheet 11 is narrower than a width W2 of the roll sheet 11.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] In an inkjet image forming apparatus, when an image is formed on roll paper, which is continuous paper wound into a roll, ink is ejected from an inkjet head onto the roll paper transported along a transport path (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-31019 A Summary of the Invention [Problem to be solved by the invention]

[0004] In inkjet image forming devices, when ink is ejected from the inkjet head toward the roll paper, the clearance between the inkjet head and the roll paper is very narrow. Meanwhile, when the roll paper is stored or installed in the image forming device, moisture absorption and desorption from the end face of the roll causes deformation at the edge in the paper width direction (hereinafter referred to as the "paper side edge"). When transporting such roll paper, the paper side edge can warp (hereinafter referred to as "edge warping"), potentially causing the roll paper to come into contact with the inkjet head during transport.

[0005] The present invention has been made to solve the above-mentioned problems, and its purpose is to provide an image forming device that can prevent roll paper from coming into contact with an inkjet head due to curling of the end of the roll paper. [Means for solving the problem]

[0006] The image forming apparatus according to the present invention includes a transport unit that transports roll paper in a transport direction along a transport path, and an image forming unit having an inkjet head that ejects ink toward an image forming surface of the roll paper transported by the transport unit. The transport unit has a pair of guide members that guide the roll paper at the ink ejection position of the inkjet head, and the guide width along which the pair of guide members guide the roll paper in a direction perpendicular to the transport direction is narrower than the width of the roll paper. [Effects of the Invention]

[0007] According to the present invention, it is possible to prevent the roll paper from coming into contact with the inkjet head due to curling of the end of the roll paper. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 5A and 5B are schematic diagrams illustrating the configuration of a pair of guide members. [Figure 3] FIG. 2 is a side view showing the configuration of a transport unit. [Figure 4] FIG. 2 is a perspective view showing the configuration of a transport unit. [Figure 5] 10A and 10B are diagrams illustrating the relationship between the guide width of the guide member and the width of the roll paper. [Figure 6] FIG. 10 is a diagram showing a first configuration example for making the guide width variable. [Figure 7] FIG. 10 is a diagram showing a second configuration example for making the guide width variable. [Figure 8] FIG. 4 is a schematic diagram illustrating a configuration of a guide width detection unit. [Figure 9] FIG. 1 is a diagram (part 1) illustrating curling at the edge of roll paper. [Figure 10] FIG. 2 is a diagram (part 2) illustrating curling at the edge of roll paper. [Figure 11] FIG. 10 is a schematic diagram showing a specific example of a warp detection unit. [Figure 12] 10A and 10B are schematic diagrams showing the amount of end warpage that can be detected by the warpage detection unit; [Figure 13] 3A and 3B are schematic diagrams showing specific examples of a warp correction unit. [Figure 14] FIG. 2 is a schematic diagram showing the configuration of a blower unit. [Figure 15] FIG. 2 is a block diagram showing a control configuration of the image forming apparatus according to the embodiment of the present invention. [Figure 16] 10A and 10B are diagrams illustrating the state of transport of roll paper in a comparative example. [Figure 17] 10A and 10B are diagrams illustrating the state of transport of roll paper in the embodiment. [Figure 18] FIG. 10 is a diagram showing a humidification table. [Figure 19] FIG. [Figure 20] FIG. 10 is a diagram illustrating a speed table. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this specification and the drawings, elements having substantially the same functions or configurations are designated by the same reference numerals, and redundant description will be omitted.

[0010] FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. 1, image forming device 10 includes a feeding section 12 that feeds out roll paper 11, a transport section 13 that transports roll paper 11 fed from feeding section 12, an image forming section 14 that forms an image on roll paper 11 transported by transport section 13, and a winding section 15 that winds up roll paper 11 on which an image has been formed by image forming section 14. Image forming device 10 is an inkjet type image forming device.

[0011] The roll paper 11 is transported from the supply unit 12 to the winding unit 15. The supply unit 12 is located at the most upstream side in the transport direction of the roll paper 11, and the winding unit 15 is located at the most downstream side in the transport direction of the roll paper 11. The transport unit 13 transports the roll paper 11 in the transport direction along a transport path 16. The transport unit 13 is equipped with a paper feed roller 17 and a paper discharge roller 18. The paper feed roller 17 is located upstream of the transport path 16. The paper discharge roller 18 is located downstream of the transport path 16. The transport path 16 is formed in a fan shape between the paper feed roller 17 and the paper discharge roller 18.

[0012] The image forming unit 14 has a plurality of inkjet heads 20. In this embodiment, an example is shown in which the image forming unit 14 has eight inkjet heads 20. The eight inkjet heads 20 correspond to a total of eight colors of ink, including, for example, five colors of white, yellow, magenta, cyan, and black, and three other colors (special colors). However, the number of inkjet heads 20 included in the image forming unit 14 may be other than eight.

[0013] The multiple inkjet heads 20 are arranged at predetermined intervals in the transport direction of the roll paper 11. The inkjet heads 20 form images on the roll paper 11 by ejecting ink toward the image-forming surface of the roll paper 11 transported by the transport unit 13. Ink for forming images may be ultraviolet-curable ink (hereafter referred to as "UV ink"), water-based ink, or the like. In this embodiment, UV ink is used as an example.

[0014] Each inkjet head 20 is positioned in a direction perpendicular to the transport direction of the roll paper 11. When forming an image on the roll paper 11, each inkjet head 20 is fixed (stationary) on the transport path 16 and positioned facing the image-forming surface 11a (see FIG. 2) of the roll paper 11. In the transport path 16, a predetermined clearance is ensured between the inkjet head 20 and the image-forming surface 11a of the roll paper 11. This clearance is set to a very small value to reduce variation in the ink landing position.

[0015] In addition to the above-mentioned paper feed roller 17 and paper discharge roller 18, the transport unit 13 also has a pair of guide members 22 as shown in Figure 2. The pair of guide members 22 are members that guide the roll paper 11 so that the image formation surface 11a of the roll paper 11 is flat at an ink ejection position 21 where the inkjet head 20 ejects ink. The ink ejection position 21 is the position where the inkjet head 20 ejects ink toward the roll paper 11 being transported in the transport direction Y.

[0016] Each of the pair of guide members 22 is formed in a roll shape. The pair of guide members 22 are arranged parallel to each other and perpendicular to the transport direction Y. Of the pair of guide members 22, one guide member 22 is arranged upstream of the ink ejection position 21 in the transport direction Y, and the other guide member 22 is arranged downstream of the ink ejection position 21 in the transport direction Y. The pair of guide members 22 are attached to a support member 23. The support member 23 is a member that supports each of the guide members 22 rotatably.

[0017] A pair of guide members 22 is provided for each inkjet head 20. In this embodiment, as described above, the image forming unit 14 has eight inkjet heads 20. Therefore, the conveying unit 13 has eight pairs of guide members 22, as shown in FIGS.

[0018] As shown in FIG. 5, in the direction X (hereafter referred to as the "CD direction") perpendicular to the conveyance direction Y, the pair of guide members 22 guide the paper roll 11 with a guide width W1 that is narrower than the width W2 of the paper roll 11. When the outer circumferential surface 22a of the guide members 22 is configured to contact the paper roll 11, the guide width W1 corresponds to the width of the outer circumferential surface 22a of the guide members 22. Therefore, when the guide width W1 of the guide members 22 is narrower than the width W2 of the paper roll 11, both widthwise ends of the paper roll 11 do not come into contact with the outer circumferential surface 22a of the guide members 22, but extend beyond the left and right edges of the outer circumferential surface 22a.

[0019] In this embodiment, the guide width W1 described above is changeable. Several configurations are conceivable for making the guide width W1 changeable. For example, as shown in FIGS. 6A and 6B, a configuration is conceivable in which guide members 22 with different widths of the roll outer peripheral surface 22a are prepared and the guide member 22 attached to the support member 23 (see FIG. 2) is replaced to change the guide width W1. Alternatively, as shown in FIG. 7, a configuration is conceivable in which the guide width W1 is changed by detachably attaching a sub-roll 24 to the rotation shaft 22b of the guide member 22. The sub-roll 24 has the same outer diameter as the roll outer peripheral surface 22a. A shaft hole is formed on the central axis of the sub-roll 24, into which the rotation shaft 22b of the guide member 22 can be inserted. The sub-roll 24 is fixed to the rotation shaft 22b with screws or the like (not shown). The sub-rolls 24 are attached in pairs, one on the left and one on the right. When the sub-roll 24 is attached to the rotary shaft 22b, the guide width W1 of the guide member 22 becomes wider, and when the sub-roll 24 is removed from the rotary shaft 22b, the guide width W1 of the guide member 22 becomes narrower.

[0020] Furthermore, in this embodiment, as shown in FIG. 8, a guide width detection unit 26 is provided that detects the guide width W1 (FIG. 5) of the guide member 22. The guide width detection unit 26 is composed of a light projector 26a and a light receiver 26b. The light projector 26a and the light receiver 26b are disposed at positions (hereinafter referred to as "detection positions") that are a predetermined distance away from the midpoint of the roll outer peripheral surface 22a in the CD direction X. For example, if the guide width W1 is changed by attaching or detaching the sub-roll 24, the detection position is set to the position where the sub-roll 24 is attached. In this case, the light projector 26a emits light 27 toward the attachment position of the sub-roll 24. The light receiver 26b receives the light emitted from the light projector 26a and switches, for example, from an off state to an on state.

[0021] When the sub-roll 24 is attached to the rotating shaft 22b of the guide member 22, the light 27 emitted from the light emitter 26a is blocked by the sub-roll 24. This causes the light receiver 26b to be in the OFF state. In contrast, when the sub-roll 24 is not attached to the rotating shaft 22b of the guide member 22, the light emitted from the light emitter 26a reaches the light receiver 26b without being blocked by the sub-roll 24. This causes the light receiver 26b to be in the ON state. Therefore, the guide width W1 can be detected based on the ON / OFF state of the light receiver 26b. Note that the guide width detection unit 26 detects the guide width after the transport unit 13, including the pair of guide members 22, has been set up and before the roll paper 11 is set in the transport path 16.

[0022] As shown in FIG. 1, the image forming apparatus 10 according to this embodiment also includes a warp detection unit 31, a warp correction unit 32, a drying unit 33, and an ink curing unit .

[0023] The warp detection unit 31 detects end warping that occurs at the widthwise ends of the roll paper 11. The warp detection unit 31 is located upstream of the image forming unit 14 in the transport direction Y. The warp detection unit 31 is also located downstream of the paper feed roller 17 in the transport direction Y.

[0024] Here, the curling of the edge of the roll paper 11 will be explained using FIGS. As shown in Figure 9, edge curl of roll paper 11 is curl that occurs at the widthwise edges (both ends) of roll paper 11. The widthwise direction of roll paper 11 is the direction perpendicular to the conveyance direction Y, i.e., corresponds to the CD direction X. Edge curl of roll paper 11 can be divided into two types depending on the direction of curl of the roll paper 11. The first type, as shown in Figure 10A, is a type in which the widthwise edges of the roll paper 11 (hereinafter simply referred to as "edges") curl upward on the conveyance path 16. The second type, as shown in Figure 10B, is a type in which the edges of the roll paper 11 curl downward on the conveyance path 16. The direction and amount of curl at the edges of roll paper 11 vary depending on the paper type, basis weight, thickness, moisture absorption of the edges, and drying conditions of the roll paper 11. Paper types for roll paper 11 include, for example, fine paper, coated paper, tack paper, and cast-coated paper.

[0025] FIG. 11 is a schematic diagram showing a specific example of the warp detection unit. As shown in FIG. 11, the warp detection unit 31 detects edge warping of the roll paper 11 as it is guided by a pair of guide rollers 36. The warp detection unit 31 is located between the pair of guide rollers 36 in the conveyance direction Y. The warp detection unit 31 is also located near the guide roller 36 that is located upstream in the conveyance direction Y. Fluttering of the roll paper 11 is suppressed near the guide rollers 36. Therefore, by having the warp detection unit 31 detect edge warping of the roll paper 11 near the guide rollers 36, the effects of fluttering of the roll paper 11 can be suppressed and edge warping of the roll paper 11 can be detected accurately. The warp detection unit 31 is configured, for example, with a laser displacement meter that irradiates the edge of the roll paper 11 with a laser from a direction perpendicular to the conveyance direction Y. As shown in FIG. 12, the warp detection unit 31 outputs a detection value related to the amount of warping (edge ​​warp amount) Z of the edge warp of the roll paper 11.

[0026] The warpage detection unit 31 is not limited to the laser displacement meter as described above, and may be configured by, for example, a two-dimensional displacement sensor or a contact-type displacement sensor.

[0027] The warp correction unit 32 corrects warping at the edges of the roll paper 11. The warp correction unit 32 is located upstream of the image forming unit 14 in the transport direction Y. The warp correction unit 32 is also located downstream of the warp detection unit 31 in the transport direction Y.

[0028] FIG. 13 is a schematic diagram showing a specific example of a warp correction unit. As shown in Figure 13, the warp correction unit 32 has a humidification mechanism 37. The humidification mechanism 37 corrects warping at the edges of the roll paper 11 by humidifying the roll paper 11 while it is being transported. The humidification mechanism 37 corrects warping at the edges of the roll paper 11 so that the edges in the width direction of the roll paper 11 move away from the inkjet head 20. The configuration of the humidification mechanism 37 will be explained below.

[0029] The humidifying mechanism 37 includes a pair of upper and lower transport rollers 41a, 41b, a supply roller 42a that supplies moisture to the upper transport roller 41a, a supply roller 42b that supplies moisture to the lower transport roller 41b, a draining roller 43a that adjusts the amount of moisture contained in the supply roller 42a, a draining roller 43b that adjusts the amount of moisture contained in the supply roller 42b, two water supply rollers 44, 45 (large and small) that supply water to the supply roller 42a, and two water storage sections 46a, 46b. Water 47a is stored in the water storage section 46a, and water 47b is also stored in the water storage section 46b.

[0030] 13, water supply roller 45 and supply roller 42a rotate counterclockwise, while water supply roller 44, draining roller 43a, and transport roller 41a rotate clockwise. Also, draining roller 43b and transport roller 41b rotate counterclockwise, and supply roller 42b rotates clockwise.

[0031] The pair of transport rollers 41a, 41b rotate while nipping the roll paper 11, transporting the roll paper 11 in the transport direction Y. In doing so, the transport roller 41a humidifies the upper surface of the roll paper 11, and the transport roller 41b humidifies the lower surface of the roll paper 11. The supply rollers 42a, 42b are each made of a soft sponge roller. The draining rollers 43a, 43b are each made of a hard sponge roller.

[0032] Supply roller 42a is provided so as to be movable toward and away from conveyor roller 41a. Supply roller 42a rotates while receiving water from water supply roller 44. The outer diameter of water supply roller 44 is larger than the outer diameter of water supply roller 45. Water supply roller 44 contacts supply roller 42a upstream of draining roller 43a in the direction of rotation of supply roller 42a. Meanwhile, water supply roller 45 contacts water supply roller 44 upstream of supply roller 42a in the direction of rotation of water supply roller 44. The lower peripheral surface of water supply roller 45 is immersed in water 47a stored in water storage section 46a.

[0033] Supply roller 42b is provided so as to be movable in a direction toward and away from conveyance roller 41b. The lower peripheral surface of supply roller 42b is immersed in water 47b stored in water storage section 46b.

[0034] The draining roller 43a rotates while contacting the supply roller 42a with a predetermined pressure. As a result, the draining roller 43a reduces the amount of moisture contained in the supply roller 42a (hereinafter also referred to as "moisture content"). The contact pressure of the draining roller 43a with respect to the supply roller 42a can be changed by a contact pressure changing mechanism (not shown). Increasing the contact pressure of the draining roller 43a with respect to the supply roller 42a increases the amount of moisture removed by the draining roller 43a, and decreasing the contact pressure of the draining roller 43a with respect to the supply roller 42a decreases the amount of moisture removed by the draining roller 43a. Therefore, by changing the contact pressure with the contact pressure changing mechanism, the moisture content of the supply roller 42a can be adjusted.

[0035] The draining roller 43b rotates while contacting the supply roller 42b at a predetermined pressure. As a result, the draining roller 43b reduces the amount of moisture contained in the supply roller 42b (hereinafter also referred to as "moisture content"). The contact pressure of the draining roller 43b with respect to the supply roller 42b can be changed by a contact pressure change mechanism (not shown). Increasing the contact pressure of the draining roller 43b with respect to the supply roller 42b increases the amount of moisture removed by the draining roller 43b, and decreasing the contact pressure of the draining roller 43b with respect to the supply roller 42b decreases the amount of moisture removed by the draining roller 43b. Therefore, by changing the contact pressure using the contact pressure change mechanism, the moisture content of the supply roller 42b can be adjusted.

[0036] The water 47a, 47b stored in each of the water storage sections 46a, 46b is pumped up by a pump from a tank (not shown). A water level sensor (not shown) is provided in the water storage section 46a, and a control section (described later) controls the operation of the pump based on the detection value of the water level sensor, thereby maintaining the amount of water stored in the water storage section 46a at a certain level or above. Similarly, a water level sensor (not shown) is provided in the water storage section 46b, and a control section controls the operation of the pump based on the detection value of the water level sensor, thereby maintaining the amount of water stored in the water storage section 46b at a certain level or above.

[0037] The humidifying mechanism 37 configured as above operates as follows. Water supply roller 45 rotates while holding water 47a stored in water storage section 46a, supplying the water 47a to water supply roller 44. Water supply roller 44 receives water 47a from water supply roller 45 and supplies the received water 47a to supply roller 42a. Supply roller 42a receives water 47a from water supply roller 44 and becomes moistened. Draining roller 43a adjusts the moisture content of supply roller 42a. Transport roller 41a receives moisture from supply roller 42a after its moisture content has been adjusted, and supplies the received moisture to the top surface of roll paper 11 to humidify roll paper 11.

[0038] Meanwhile, supply roller 42b rotates while containing water 47b stored in water storage section 46b. Draining roller 43b adjusts the moisture content of supply roller 42b. Transport roller 41b receives moisture from supply roller 42b after adjusting its moisture content, and supplies the received moisture to the underside of roll paper 11 to humidify the roll paper 11.

[0039] The warp correction unit 32 corrects the warp at the end of the roll paper 11 by operating the humidification mechanism 37 described above, so that the widthwise end of the roll paper 11 moves away from the inkjet head 20. Specifically, if the end of the roll paper 11 is warped upward as shown in Figure 10A above, the warp at the end of the roll paper 11 is corrected so that the end of the roll paper 11 warps downward as shown in Figure 10B.

[0040] The drying section 33 dries the roll paper 11 that has been humidified by the humidifying mechanism 37 of the warp correction section 32. The drying section 33 is located upstream of the image forming section 1421 in the transport direction Y. The drying section 33 is also located downstream of the humidifying mechanism 37 in the transport direction Y. The drying section 33 dries the roll paper 11 by blowing air. The drying section 33 is equipped with multiple air blowing units 35. The multiple air blowing units 35 are arranged at predetermined intervals in the transport direction Y. The number of air blowing units 35 that the drying section 33 has can be changed (increased or decreased) as needed.

[0041] As shown in Figure 14, the air blowing units 35 are arranged in pairs, one above the other. The upper air blowing unit 35 is arranged facing the top surface of the roll paper 11, and the lower transport unit 35 is arranged facing the bottom surface of the roll paper 11. The air blowing units 35 have a fan 35a and a heater 35b. The fan 35a blows air toward the roll paper 11. The heater 35b warms the air blown by the fan 35a. In this way, the air blowing unit 35 dries the roll paper 11 with warm air. Note that the air blowing units 35 may be arranged in a pair above and below at only one location in the transport direction Y, as shown in Figure 14.

[0042] FIG. 15 is a block diagram showing the control configuration of the image forming apparatus according to the embodiment of the present invention. In FIG. 15 , a control unit 50 comprehensively controls the operation of the entire image forming apparatus 10. The control unit 50 controls the operation of each unit, including the above-mentioned conveying unit 13, image forming unit 14, warp correction unit 32, and drying unit 33. The control unit 50 includes a central processing unit (CPU), read-only memory (ROM), and random access memory (RAM) (not shown) as computer hardware resources. The CPU reads a predetermined program from the ROM, loads it into the RAM, and controls the operation of each unit of the image forming apparatus 10 in accordance with the loaded program. The control unit 50 is connected to a system bus 55 along with an image input unit 51, an image processing unit 52, an operation display unit 53, and a storage unit 54. The system bus 55 is also connected to the above-mentioned conveying unit 13, image forming unit 14, guide width detection unit 26, warp detection unit 31, warp correction unit 32, drying unit 33, etc.

[0043] The image input unit 51 inputs image data to be used for image formation. The image input unit 51 is composed of, for example, a communication interface, an image scanner, a memory interface, and the like. The communication interface is an interface that receives image data sent from an external device (not shown) via a network. The image scanner is a scanner that optically reads an image recorded on an original (not shown). The memory interface is an interface that reads image data from a storage medium (not shown).

[0044] The image processing unit 52, under the control of the control unit 50, performs predetermined image processing (tone correction, color correction, shading processing, enlargement / reduction processing, etc.) on the image data input by the image input unit 51.

[0045] The operation display unit 53 is a section for inputting and displaying various settings and conditions relating to image formation, etc. The operation display unit 53 is configured by, for example, a display with a touch panel.

[0046] The storage unit 54 is configured by, for example, a nonvolatile semiconductor memory (so-called flash memory), a hard disk drive (HDD), a solid state drive (SSD), etc. The storage unit 54 stores image data and the like to be used for image formation. The storage unit 54 also stores various types of data that the control unit 50 references when controlling the operation of each unit of the image forming apparatus 10.

[0047] Next, the operation and functions of the image forming apparatus 10 according to the embodiment of the present invention will be described. First, the basic operation of the image forming apparatus 10 will be described. As shown in Figure 1, roll paper 11 is set in image forming apparatus 10. At this time, roll paper 11 is attached to feeding section 12. One end of roll paper 11 in the longitudinal direction is attached to winding section 15 via transport path 16.

[0048] The roll paper 11 set as described above is fed from the feeding unit 12. In this embodiment, the roll paper 11 is transported roll-to-roll and is transported in the transport direction Y (FIG. 2) along the transport path 16. When this happens, if the transport path 16 is formed in a fan shape, tension is applied to the roll paper 11 along the fan-shaped transport path 16, which has the effect of suppressing curling of the roll paper 11.

[0049] An image is formed on the roll paper 11 transported along the transport path 16 by the image forming unit 14. At this time, the control unit 50 controls the driving of the transport unit 13, thereby controlling the transport of the roll paper 11. The control unit 50 also controls the driving of multiple inkjet heads 20 provided in the image forming unit 14, thereby causing ink to adhere to the image formation surface 11a of the roll paper 11.

[0050] The roll paper 11, on which an image has been formed by adhering ink, is sent to the ink curing unit 34. The ink curing unit 34 irradiates the roll paper 11 with ultraviolet light, which hardens the ink adhering to the roll paper 11. The roll paper 11 with the image formed thereon is then taken up by the take-up unit 15 via the paper discharge rollers 18. The basic operation of the image forming apparatus 10 has been described above.

[0051] In the image forming apparatus 10 according to this embodiment, as shown in Figure 5, the guide width W1 defined by the pair of guide members 22 is narrower than the width W2 of the roll paper 11. In this case, it is preferable that the guide width W1 defined by the pair of guide members 22 is wider than the maximum image formation width of the roll paper 11. The maximum image formation width is set to be equal to or smaller than the width W2 of the roll paper 11. The maximum image formation width may be set in advance by the user using the operation and display unit 53.

[0052] Alternatively, the control unit 50 may automatically set the maximum image formation width based on the guide width W1 detected by the guide width detection unit 26. In this case, the control unit 50 calculates the maximum image formation width based on the guide width W1 detected by the guide width detection unit 26 as follows. For example, if the maximum image formation width (mm) is defined as W3 (mm), the control unit 50 calculates the maximum image formation width by calculating "W3 = W1 - Δw" so that the maximum image formation width W3 is narrower than the guide width W1. As a result, if Δw = 20 (mm), for example, the maximum image formation width is defined as a position 10 (mm) inward from the left and right ends of the roll outer peripheral surface 22a. The value of Δw can be set or changed by the user, for example, by operating the operation and display unit 53.

[0053] Before the image forming unit 14 starts image formation, the control unit 50 performs the following process. First, the control unit 50 determines the width of the image to be formed on the roll paper 11 based on the image data processed by the image processing unit 52. Next, the control unit 50 compares the determined image width with the maximum image formation width W3. Next, the control unit 50 allows the image forming unit 14 to form an image if the determined image width is equal to or smaller than the maximum image formation width W3. Furthermore, the control unit 50 prohibits the image forming unit 14 from forming an image if the determined image width exceeds the maximum image formation width W3. When prohibiting image formation, the control unit 50 displays an error screen on the operation display unit 53. The error screen may include an error message indicating that the image width exceeds the maximum image formation width, as well as a layout rearrangement instruction to redo the image layout.

[0054] As a comparative example, if the guide width W1 defined by the pair of guide members 22 is equal to or less than the width W2 of the paper roll 11, the following problem may occur: If the end of the paper roll 11 unwound from the unwinding unit 12 curls as shown in FIG. 10B, the end of the paper roll 11 will climb onto the outer circumferential surface 22a of the roll, causing the surface of the paper roll 11 to lift off the outer circumferential surface 22a of the guide members 22, as shown in FIG. 16. This could cause the paper roll 11 to come into contact with the inkjet head 20.

[0055] In contrast, in this embodiment, when the guide width W1 defined by the pair of guide members 22 is shorter than the width W2 of the paper roll 11, the edges of the paper roll 11 extend beyond the left and right edges of the outer circumferential surface 22a of the roll, as shown in Figure 17. This allows the paper roll 11 to be guided by the guide members 22 without lifting up from the outer circumferential surface 22a. This means that the paper roll 11 can be transported without coming into contact with the inkjet head 20.

[0056] Furthermore, if the end of the roll paper 11 unwound from the unwinding unit 12 is warped as shown in FIG. 10A, the roll paper 11 is guided by the guide member 22 without lifting off the outer circumferential surface 22a of the roll. However, the end of the roll paper 11 warps in the direction toward the inkjet head 20. This could cause the end of the roll paper 11 to come into contact with the inkjet head 20. Therefore, the warp correction unit 32 corrects the end warp of the roll paper 11 so that the end of the roll paper 11 moves away from the inkjet head 20. As a result, even when handling roll paper 11 that is warped as shown in FIG. 10A, the roll paper 11 will look like FIG. 17 after being straightened by the warp correction unit 32. This makes it possible to prevent the roll paper 11 from coming into contact with the inkjet head 20. Specific processes for correcting end warp in roll paper 11 are described below.

[0057] First, the roll paper 11 is fed from the feed unit 12 to the transport path 16 and passes through the warp detection unit 31 via the paper feed roller 17. At this time, the warp detection unit 31 detects the edge warp of the roll paper 11. The warp detection unit 31 also detects the direction and amount of warp at the edge of the roll paper 11. This makes it possible to detect the amount of warp when the edge of the roll paper 11 is warped as shown in Figure 10A. The detection results of the warp detection unit 31 are input into the control unit 50. The control unit 50 then controls the humidification mechanism 37 of the warp correction unit 32 to operate if the edge of the roll paper 11 is warped as shown in Figure 10A and the amount of warp exceeds the predetermined value, causing the humidification mechanism 37 to operate and humidify the roll paper 11. As a result, the roll paper 11 is transported either without warp or with warp as shown in Figure 17. The predetermined value is set to a value smaller than the clearance secured between the inkjet head 20 and the roll paper 11 so that the edge of the roll paper 11 does not come into contact with the inkjet head 20 .

[0058] The humidification conditions applied to the humidification mechanism 37 are controlled by the control unit 50, for example, according to the humidification table shown in FIG. 18. This humidification table is stored in the memory unit 54. In the humidification table shown in FIG. 18, the amount of moisture supplied to the roll paper 11 by the humidification mechanism 37 (hereinafter also referred to as "humidification amount") is divided into three levels: "large," "medium," and "small." "Large" indicates the highest humidification amount. "Small" indicates the lowest humidification amount. "Medium" indicates the humidification amount is less than "large" but more than "small."

[0059] The control unit 50 determines the basis weight (g / m 2 ) and the amount of curl (mm) at the end of the roll paper 11. For example, the control unit 50 controls the amount of humidification by the humidifying mechanism 37 based on the basis weight of the roll paper 11 being between 109 and 158 (g / m 2 ), and if the amount of edge warping is 3 to 5 (mm), the controller 50 controls the warping correction unit 32 so that the amount of humidification by the humidifying mechanism 37 is "low." Also, if the basis weight of the roll paper 11 is 210 to 256 (g / m 2 ), and if the end curl is 3 to 5 mm, the controller 50 controls the curl correction unit 32 so that the humidification amount by the humidification mechanism 37 is "medium." Also, if the basis weight of the roll paper 11 is 257 to 400 (g / m 2 ), if the amount of end warping is 7 to 10 mm, the warping correction unit 32 is controlled so that the amount of humidification by the humidification mechanism 37 is "high." This allows the amount of humidification to be adjusted appropriately according to the characteristics of the roll paper 11 being used.

[0060] In this embodiment, the amount of humidification by the humidification mechanism 37 is controlled based on the basis weight and amount of edge curl of the paper roll 11, but the present invention is not limited to this. It is also possible to adopt a configuration in which the amount of humidification by the humidification mechanism 37 is controlled based on at least one of the paper type, basis weight, thickness, and amount of edge curl of the paper roll 11. The paper type and / or basis weight of the paper roll 11 may be specified by the user using, for example, the operation and display unit 53. The thickness of the paper roll 11 may be specified by the user using, for example, the operation and display unit 53, or may be detected using a paper thickness sensor (not shown) or the like.

[0061] The humidification conditions applied to the humidification mechanism 37 may also change if the type of roll paper 11 loaded in the image forming apparatus 10 changes. The humidification conditions are set, for example, using the following procedure: First, the supply roller 42a is separated from the conveyance roller 41a. Next, the contact pressure of the draining roller 43a is changed to adjust the moisture content of the supply roller 42a. After a certain period of time, the supply roller 42a is brought into contact with the conveyance roller 41a. Similarly, the supply roller 42b is separated from the conveyance roller 41b. Next, the contact pressure of the draining roller 43b is changed to adjust the moisture content of the supply roller 42b. After a certain period of time, the supply roller 42b is brought into contact with the conveyance roller 41b. The roll paper 11 is then fed empty until the amount of moisture added to the roll paper 11 by the conveyance rollers 41a and 41b stabilizes. Once the moisture content stabilizes, image formation begins.

[0062] In addition, when the humidifying mechanism 37 humidifies the roll paper 11 and the end of the roll paper 11 is bent away from the inkjet head 20, the mechanism described above using Figure 17 can prevent the roll paper 11 from coming into contact with the inkjet head 20.

[0063] The roll paper 11, moistened as described above, passes through the drying unit 33 before being fed into the image forming unit 14. At this time, the drying unit 33 dries the roll paper 11 by blowing air. At this time, the control unit 50 controls the drying conditions for the roll paper 11 by the drying unit 33 as follows.

[0064] The control unit 50 controls the drying conditions applied to the drying unit 33, for example, in accordance with a drying table shown in FIG. 19. This drying table is stored in the memory unit 54. In the drying table shown in FIG. 19, the drying conditions for the drying unit 33 are categorized by a combination of the airflow rate of the fan 35a and the output of the heater 35b. The airflow rate of the fan 35a is expressed as a percentage of the maximum airflow rate of the fan 35a, which is 100%. Specifically, the notation "F:60" indicates that the airflow rate of the fan 35a is 60% of the maximum airflow rate, the notation "F:80" indicates that the airflow rate of the fan 35a is 80% of the maximum airflow rate, and the notation "F:100" indicates that the airflow rate of the fan 35a is the maximum airflow rate (100%). Meanwhile, the output of the heater 35b is divided into three levels: Low, Middle, and High. Specifically, the notation "H:L" indicates that the heater 35b output is low, the notation "H:M" indicates that the heater 35b output is medium, and the notation "H:H" indicates that the heater 35b output is high. Furthermore, the absence of any of the notations "H:L," "H:M," and "H:H" indicates that the heater 35b output is zero, that is, drying is performed using only the airflow from the fan 35a.

[0065] The control unit 50 determines the basis weight (g / m 2 ) and the amount of curl (mm) at the end of the roll paper 11. For example, the control unit 50 controls the drying conditions for the roll paper 11 based on the basis weight of the roll paper 11 between 109 and 158 (g / m 2 ), and the amount of end curl is 3 to 5 (mm), the control unit 50 controls the air blowing unit 35 of the drying section 33 so that the air volume of the fan 35a is the maximum air volume (100%). 2 ), and the amount of end warping is 3 to 5 (mm), the control unit 50 controls the air blowing unit 35 of the drying section 33 so that the air volume of the fan 35a is 80% of the maximum air volume and the output of the heater 35b is medium. Also, the control unit 50 controls the roll paper 11 so that the basis weight is 257 to 400 (g / m 2), and if the amount of end warping is 7 to 10 mm, the blower unit 35 of the drying section 33 is controlled so that the air volume of the fan 35a is 80% of the maximum air volume and the output of the heater 35b is High. This makes it possible to adjust the drying conditions appropriately according to the characteristics of the roll paper 11 being used.

[0066] In this embodiment, an example has been shown in which the drying conditions by the drying unit 33 are controlled based on the basis weight and amount of end curl of the roll paper 11, but the present invention is not limited to this, and a configuration may be adopted in which the drying conditions by the drying unit 33 are controlled based on at least one of the paper type, basis weight, thickness, and amount of end curl of the roll paper 11. The drying conditions may also be controlled based on the temperature and / or humidity of the environment in which the image forming apparatus 10 is installed.

[0067] The roll paper 11 dried as described above is sent to the image forming unit 14. The control unit 50 controls the driving of each inkjet head 20. The control unit 50 also controls the transport speed of the roll paper 11 by the transport unit 13 as follows.

[0068] The speed conditions applied to the transport speed of the roll paper 11 are controlled by the control unit 50, for example, according to the speed table shown in Fig. 20. This speed table is stored in the memory unit 54. In the speed table shown in Fig. 20, the transport speed of the roll paper 11 by the transport unit 13 is divided into three stages. The first transport speed is a speed equivalent to 1 / 1 of the reference transport speed, the second transport speed is a speed equivalent to 2 / 3 of the reference transport speed, and the third transport speed is a speed equivalent to 1 / 2 of the reference transport speed.

[0069] The control unit 50 determines the basis weight (g / m 2 ) and the amount of curl (mm) at the end of the roll paper 11. For example, the control unit 50 controls the speed at which the roll paper 11 is conveyed by the conveyance unit 13 based on the basis weight of the roll paper 11 between 109 and 158 (g / m 2), and the amount of edge curl is 3 to 5 (mm), the control unit 50 controls the conveyance unit 13 so that the conveyance speed of the roll paper 11 is 1 / 1 of the standard conveyance speed. 2 ), and the amount of edge curl is 3 to 5 (mm), the control unit 50 controls the conveyance unit 13 so that the conveyance speed of the roll paper 11 is 2 / 3 times the standard conveyance speed. 2 ), if the amount of edge warping is 7 to 10 mm, the conveying unit 13 is controlled so that the conveying speed of the roll paper 11 is half the standard conveying speed. This allows the conveying speed to be adjusted appropriately according to the characteristics of the roll paper 11 being used.

[0070] In this embodiment, an example is shown in which the transport speed of the roll paper 11 by the transport unit 13 is controlled based on the basis weight and end curl amount of the roll paper 11, but the present invention is not limited to this, and a configuration may be adopted in which the transport speed of the roll paper 11 by the transport unit 13 is controlled based on at least one of the paper type, basis weight, thickness, and end curl amount of the roll paper 11.

[0071] <Modifications, etc.> The technical scope of the present invention is not limited to the above-described embodiments, but also includes forms in which various modifications and improvements are made within the scope that can derive specific effects obtained by the constituent elements of the invention and their combinations.

[0072] For example, in the above embodiment, the transport path 16 for the roll paper 11 is formed in a fan shape as a preferred example, but the present invention is not limited to this and may be applied to an image forming apparatus having a transport path other than a fan shape. [Explanation of symbols]

[0073] 10...Image forming device 11...Roll paper 11a...Image formation surface 13...Transportation section 14...Image forming unit 16...Transport path 20...Inkjet head 21...Ink injection position 22...Guide member 26...Guide width detector 31...Warp detection unit 32...Curving section 33...Drying section 35...Blower unit 35a...Fan 35b...Heater 37…humidification mechanism Y: Transport direction X...CD direction (width direction of roll paper)

Claims

1. a conveying unit that conveys the roll paper in a conveying direction along a conveying path; an image forming unit having an inkjet head that ejects ink toward an image forming surface of the roll paper that is transported by the transport unit, the transport unit has a pair of guide members that guide the roll paper at a position where ink is ejected by the inkjet head; a guide width by which the pair of guide members guide the roll paper in a direction perpendicular to the transport direction is narrower than the width of the roll paper; The guide width is variable Image forming device.

2. The guide width is wider than the maximum image forming width of the roll paper. The image forming apparatus according to claim 1 .

3. a guide width detection unit that detects the guide width defined by the pair of guide members; a control unit that determines a maximum image formation width based on the guide width detected by the guide width detection unit, and prohibits image formation when the width of the image to be formed on the roll paper exceeds the maximum image formation width. The image forming apparatus according to claim 1 .

4. The conveying path is fan-shaped The image forming apparatus according to claim 1 .

5. A warp correction unit that corrects end warp that occurs at an end of the roll paper in the width direction is provided upstream of the image forming unit in the transport direction. The image forming apparatus according to claim 1 .

6. The warp correction unit has a humidifying mechanism that humidifies the roll paper. The image forming apparatus according to claim 5 .

7. a warp detection unit that detects end warp of the roll paper is provided upstream of the warp correction unit in the conveyance direction, The humidifying mechanism operates when the detection value of the end warp detected by the warp detection unit exceeds a predetermined value. The image forming apparatus according to claim 6 .

8. The warp correction unit corrects the end warp so that the end of the roll paper in the width direction moves away from the inkjet head. The image forming apparatus according to claim 5 .

9. A drying unit that dries the roll paper is provided upstream of the image forming unit in the transport direction and downstream of the humidifying mechanism in the transport direction. The image forming apparatus according to claim 6 .

10. The drying unit dries the roll paper by blowing air. The image forming apparatus according to claim 9 .

11. The drying section includes a blower unit having a fan and a heater. The image forming apparatus according to claim 10.

12. a control unit that controls the amount of humidification by the humidifying mechanism based on at least one of the paper type, basis weight, thickness, and end curl amount of the roll paper; The image forming apparatus according to claim 6 .

13. a control unit that controls the transport speed of the roll paper based on at least one of the paper type, basis weight, thickness, and end curl amount of the roll paper; The image forming apparatus according to claim 1 .

14. a control unit that controls the drying conditions of the drying unit based on at least one of the paper type, basis weight, thickness, and end curl amount of the roll paper; The image forming apparatus according to claim 10.

Images